The invention relates to a passive semiconductor power limiter, constructed on flat structure lines. The user of such a limiter is particularly advantageous in an ultra-high frequency receiver formed of transistor amplifiers or mixers constructed with micro-strip technology. Limiters in accordance with the invention may also serve for forming duplexers whose role is important in electromagnetic detection equipment or radar.
In the electromagnetic detection equipment or radar to which the present invention more particularly applies, the protection of the receiver of the radar against the transmissions of its own transmitter or of neighboring transmitters has posed a problem to which particular attention has been paid from the outset.
The protection of radar receivers was first of all ensured by gas tubes, called TR tubes which, inserted in the reception chain had the structure of a pass-band filter and the property of being conductive when the ultra-high frequency energy applied was low and reflecting when this energy exceeded a few peak watts. These tubes (which moreover gave satisfaction) presented disadvantages due to a limited life-span and a slight delay on ignition, thus letting through a part of the power towards the receiver which results in damage.
The appearance of P.I.N. diodes enabled in some cases these gas tubes to be replaced by more reliable switches insofar as the life-span was concerned. However, it is necessary to associate with these PIN diodes a control circuit in order to make them conductive a little before transmission by means of an auxiliary biasing source and so as to apply thereto a reverse voltage so as to reduce the losses at the time of reception. These control circuits being synchronous with the radar transmission, the PIN diode switches protect rather well the radar receiver from its own transmitter, but do not protect it however from neighboring transmitters.
Finally, the use of diodes specially designed and associated in pairs has allowed a solid-state protection device to be constructed, which is entirely passive and able to withstand powers of ten or so peak kilowatts. However the construction of this type of limiter on a strip line, requiring the use of two diodes mounted head-to-tail in the same case or on the same support, is very delicate.
Since the use of a passive limiter constructed with a flat structure is particularly advantageous for its integration in a receiver formed of transistor amplifiers or mixers constructed with micro-strip technology for example, the invention aims at remedying the above-mentioned constructional disadvantages.